Microhardness Values Research Articles

Physical, structural and elastic properties of Fe2O3-doped oxyfluoroborate glasses

A series of Fe2O3-doped oxyfluoroborate 75B2O3–20NaF–5BaO glasses (Fe2O3 = 0, 2, 4, and 6 mol) were synthesized using the conventional melt-quenching method. The effect of Fe2O3 on the physical, structural, and elastic characteristics of synthesized glass samples has been studied. The non-crystalline characteristics of the prepared glass samples were validated through XRD analysis, while their structural properties were examined using FTIR spectroscopy. Elastic properties were investigated through the measurement of longitudinal and shear ultrasonic velocities, employing the pulse-echo technique. The observed density and computed molar volume were determined to be influenced by the content of Fe2O3. The ultrasonic velocities, elastic moduli, micro-hardness, and Debye temperature exhibited similar behavior across all glass compositions, showing an increase with increasing Fe2O3 content. The findings are analyzed concerning the alteration in the topology of the borate network. The incorporation of Fe2O3 led to the transformation of BO3 structural groups into BO4 structural groups, enhancing the network connectivity and increasing the rigidity of the glass structure and elastic moduli. A variety of compositional parameters, including the average separation between boron ions, mean atomic volume, glass packing density, dissociation energy per unit volume, and excess molar volume, were assessed in concerning Fe2O3 content. These parameters were then correlated with the elastic properties, drawing on established models and theories within the discipline. The theoretical elastic moduli, micro-hardness, and Poisson's ratio values were ultimately calculated and compared with the experimental ones.

In vitro evaluation of dye penetration and dentin microhardness after laser irradiation using photon-induced photoacoustic streaming and shock wave enhanced emission photoacoustic streaming tips compared to ultrasonic activation

The purpose of this study was to compare the penetration of methylene blue (MB) dye after laser irradiation using PIPS (photon-induced photoacoustic streaming) and SWEEPS (shockwave enhanced emission photoacoustic streaming) methods compared to Passive ultrasonic irrigation (PUI) and to study their effect on dentin microhardness. A total of 44 single-rooted human teeth which were extracted for orthodontic or periodontal reasons were used. The teeth were decapitated to standardize roots to 12 mm in length. Canals were prepared up to size #30.6% and divided randomly into four groups (n = 11/group) according to the method of NaOCl activation: Group I: Er: YAG laser activation with PIPS tip; Group II: Er: YAG laser activation with SWEEPS tip; Group III: passive ultrasonic irrigation (PUI) and Group IV: conventional needle irrigation (CI). MB dye was injected then teeth were sectioned horizontally into coronal, middle and apical sections. Penetration depth/area percentages were measured using stereomicroscopy. Coronal specimens were further subjected to Vickers microhardness testing. Data were statistically analyzed. SWEEPS and PIPS activation methods provided higher dye penetration depth and area percentages compared to PUI with no statistically significant differences between all test groups. However, all test groups showed statistically significant differences with the CI (control) group. SWEEPS activation provided higher microhardness values with statistically significant differences with the other groups. Laser irrigant activation using PIPS and SWEEPS is comparable to PUI concerning MB dye penetration. However, SWEEPS preserved dentin microhardness significantly which can be beneficial for the long-term prognosis of root canal treated teeth.

Photochemically Activated Microbubble Emulsion, Nd: Yap Laser, and Cerium Oxide Nanoparticles as Canal Disinfectants on Push-Out Bond Strength of Sealer to Root Dentin, Smear Layer, and Antibacterial Efficacy.

Effect of different root canal irrigation regimes microbubble emulsion (MBE) via riboflavin photosensitizer (RFP), cerium oxide (CeO2) nanoparticles (NPs), and Nd: YAP laser on antibacterial efficiency, microhardness (MH), smear layer (SL) removal efficacy, and push-out bond strength (PBS) of AH plus sealer to canal dentin. Sixty single-rooted teeth were selected, disinfected, and categorized into four groups based on the type of disinfection. Following disinfection, a pair of samples were randomly selected and visualized under scanning electron microscope (SEM) for SL evaluation. Three samples from each disinfection group were mounted on a Vickers MH tester for hardness testing. A brain-heart infusion (BHI) agar plate was inoculated with a single colony of Enterococcus faecalis (E. faecalis), and their survival rate was measured following different disinfecting regimes. The remaining samples were filled with gutta-percha (GP) and sectioned to evaluate PBS via universal testing machine (UTM), followed by failure analysis. Data were analyzed using analysis of variance (ANOVA) and Tukey's post hoc test. The survival rate of E. faecalis was lowest for Group 3 (0.11 CFU/mL) with the highest MH values (49.72 ± 1.02 N/mm2). The PBS was highest for Group 3 cervical (11.54 ± 0.49 MPa) and middle third (11.12 ± 0.50 MPa). SL removal efficacy was comparable in groups 3 and 4 at the coronal and middle third. The application of CeO2NPs as a canal irrigant in conjunction with EDTA resulted in enhanced bond values, demonstrating superior SL removal capabilities. This type of disinfection notably enhances the MH of canal dentin while demonstrating significant sterilization efficacy against E. faecalis.

Effect of antacid gastric syrups on surface properties of dental restorative materials: an in vitro analysis of roughness and microhardness

SummaryObjectivesThe aim of this in-vitro study was to evaluate the effects of antacid gastric syrups on the surface roughness and microhardness of restorative dental materials.Materials and methodsThree different composite resins, nanohybrid, microhybrid and giomer, and four antacid gastric syrups were used in the study. A total of 150 samples were obtained by preparing 50 (10 mm x 2 mm) disk-shaped samples of each composite type. The composites were randomly divided into 5 subgroups and immersed in antacid syrups for 2 min every day for 28 days. The control group samples were kept in distilled water for 28 days. Surface roughness was measured at the beginning, on the 7th, 15th and 28th days using a mechanical profilometer, AFM, and SEM and microhardness was measured using a Vickers device. Shapiro-Wilk, Repeated Measures ANOVA, One-Way ANOVA, Tukey and Games-Howell tests were applied for statistical analysis.ResultsAfter 28 days, the surface roughness of the giomer composite decreased significantly (p < 0.05). The surface roughness of microhybrid and nanohybrid composites increased slightly but not significantly (p > 0.05). Microhardness values of microhybrid and giomer composites showed a significant decrease (p < 0.05). SEM and AFM results were in agreement with the mechanical profilometer findings.ConclusionAgents such as calcium carbonate, sodium bicarbonate and magnesium carbonate in antacid gastric syrups can affect the surface properties of restorative dental materials. This may adversely affect the longevity and aesthetics of restorations.Clinical significanceThe study emphasizes the need for caution in restorative material selection and care protocols in patients using antacid gastric syrups.

On the surface characterization of laser treated DIN 1.2379 tool steel

The following study aimed to optimize CO2 laser processing parameters for 1.2379 cold work tool steel to improve its surface properties. As its applications required high durability, strength, and precision, surface roughness and microhardness values were adjusted by varying laser power from 70% to 92%, laser speed from 1 to 5 mm/s, and stand-off distance from 4 to 6 mm. Using these background procedures, this specific study was performed to improve the manufacturing of tool steels used under extreme conditions. Scanning electron microscopy and profilometry were used to identify optimal settings that significantly improved the steel’s surface and subsurface appearances. A speed of 3 mm/s with a power of 81% and a stand-off distance of 5 mm resulted in minimized kerf width, kerf morphology, and spacing and improved uniformity. Using the energy dispersive x-ray spectrum, changes also measured in the distribution of elements, such as the increase in iron and chromium at the surface level of the steel. The effect of the parameters was quantified using analysis of variance (ANOVA) and the Taguchi method, which showed us the proportion of variance that could be described by the amount and specific parameters, with stand-off having the most impact. In this study, the specific effects of certain laser parameters on the microstructural and mechanical properties of cold work tool steel 1.2379 were recorded.

Studies of a saturated chrome layer on the surface of steel under plasma heating

In this paper, the possibility of saturation of the surface of low-carbon steels with chromium during plasma heating is considered. The analysis of existing methods of surface chrome plating of metals is carried out. The mechanism of diffusion saturation of metal with chromium can be considered as a complex process consisting of separate stages: formation of active chromium atoms near the surface or directly on the metal surface; sorption of atoms by the metal surface; diffusion of chromium atoms into the metal. The results of preliminary experiments on chrome plating of the surface layer using plasma heating are presented. In this experiment, under the action of a plasma arc, the following reactions are possible: the reduction of chromium from chromium oxide with the formation of chromium carbides Cr7C3 and Cr23C6; the formation of complex carbide-cementites (Fe, Cr)3C or (Cr, Fe)23C6. The authors proceeded from the hypothesis that if the amount of chromium in the hardened layer is in the range of 0.3–0.5% (based on X-ray analysis), therefore, in this case all chromium atoms exist in the form of a solid solution. It is known that chromium has an atomic radius r = 0.128 nm, close to the radius of iron r = 0.126 nm, but much larger than the radius of carbon r = 0.07 nm. Thus, the presence of a chromium atom together with a carbon atom in the α-lattice of iron increases the strength of the martensite lattice due to solid-phase hardening, and consequently the microhardness increases (up to 12,000 MPa). Such quantitative values of microhardness are not obtained by other cementation methods. It is proved that saturation of the metal surface with chromium from the paste during plasma heating can lead to the formation of a diffusion chrome-plated layer of steel. New additional studies of the surface layer structure and analysis of the parameters of plasma surface chrome treatment processes will be required in order to achieve the formation of high-quality chrome plating of the surface by creating a coating.

Microstructural and mechanical properties of boron carbide (B4C) coated RDSO wear plate sample

In this research, a comparative investigation was carried out on the microstructural and mechanical characteristics of boron carbide (B4C) coated RDSO (Research design & standard organization, India) approved steel sample and uncoated RDSO steel samples intended for applicable as wear plates of ballast cleaning machines which is a railways track maintenance machine. Wear plates of ballast cleaning machines are subjected to extreme abrasion & impact stresses because they directly come in contact with railways ballast. Microstructural examinations were performed using scanning electron microscopy (SEM) and optical microscope to characterize the coating’s homogeneity, adhesion, and interfacial bonding with the steel substrate. Mechanical tests, including hardness testing, tensile strength, and wear tests, were conducted to understand the coated sample’s performance compared to the uncoated counterpart. Results indicated that the average micro-hardness values, 428 ± 10 HV and 302 ± 10 HV was obtained using Vickers hardness test done on the samples B4C coated RDSO sample and uncoated RDSO sample respectively. The average coefficient of friction (COF) for the carbide-coated sample was 0.33 under a 10 N load, while the uncoated sample had a COF of 0.64. This demonstrates that the carbide coating greatly improves wear performance. This comparative analysis suggests that B4C-coated steel is a promising railways for wear plate applications in ballast cleaning machines, providing increased lifespan and better performance.

Effect of Gastric Acid on the Surface Properties of Different Composite Resin Restorative Materials: Scanning Electron Microscope (SEM) Evaluation

Objective: The aim of this study was to evaluate the effect of gastric acid on different resin-based composites with surface microhardness, surface roughness and scanning electron microscopy (SEM). Methods: Three different composite resin restorative materials (Clearfil Majesty ES-2{Kuraray, Tokyo, Japan}, Beautifil II {Shofu, Ratingen, Germany}, Group Beautifil II LS {Shofu, Ratingen, Germany}) were used. Vickers microhardness and surface roughness measurements were evaluated at baseline, after 7 and 14 days of soaking in gastric acid. SEM images were obtained to examine the effects of gastric acid on the surface properties of the composites. Results: When the difference in the microhardness values of the composite resins was compared, the time-dependent change in all composites was found to be statistically significant. The most surface roughness and hardness changes occurred in Beautifil II group (P:0.000; P&amp;lt;.05). According to SEM images, Beautifil II group was most affected by gastric acid, while Clearfil Majesty group was least affected. Conclusion: In vitro conditions gastric acid increased the surface roughness of different composites while decreasing their microhardness. As a result, if these restorative materials are to be preferred in patients with reflux, they should be checked frequently. In the presence of an uncontrollable situation, the use of these restorative materials can be limited. Keywords: Gastric acid, microhardness, surface roughness, SEM

Structural and property investigation of ceramic composite coating fabricated on titanium alloys by high power diode laser alloying

The laser alloying technique is proposed and demonstrated to synthesize titanium silver nitride-based (Ti-Ag-N, TiN/TiAg) composite coating on Ag electroplated Cp-Ti and Ti6Al4V substrates under nitrogen shielding. The laser alloying was carried out using a continuous wave mode fiber coupled diode laser at 980 nm laser wavelength. Nitrogen shielding was useful to avoid interference from atmospheric oxygen and induce the formation of titanium nitride (TiN) phases. The formation of the TiN/TiAg composite was confirmed through surface morphology studies. The microstructural features and microhardness values (around 1000 HV0.2) confirmed the formation of composite Ti-Ag-N phases in the titanium alloy surface. In Ti6Al4V substrate laser alloyed with Ag and N, the formation of dendrites and columnar growth of the composite phases were observed. Ag was homogeneously distributed in the Ti/Ni matrix, and as the Ag coating thickness increased, the average microhardness of the laser alloyed coating decreased slightly.

Influence of Laser Shock Peening on the Bobbin Tool Friction Stir-Welded AW6060 Alloy.

Friction stir welding (FSW) is a solid-state welding process that uses a rotating tool to soften and stir the base metal, thereby joining it. A special type of tool that has attracted the interest of researchers is the so-called bobbin tool (BTFSW), which, unlike conventional tools with one shoulder, features two shoulders that envelop the base metal from both the top and bottom sides. As a result, significant tensile stresses develop on both sides of the weld, caused by the action of both tool shoulders. In this paper, this issue was addressed by applying laser shock peening (LSP), aiming to introduce compressive stresses, which can be useful as a post-processing technique for BTFSW on both weld sides. It was found that this process completely alters residual stresses in the treated area, from tensile to compressive, through shock waves that impart plastic deformation in the surface layer. It was shown that the LSP effect is more pronounced as the accumulated energy is higher. As a consequence, the microhardness values were significantly increased in the surface and subsurface layers, reaching a maximum depth of 480 to 780 µm for the lowest and highest accumulated laser energy, respectively, while surface roughness increased. While increasing compressive stresses and microhardness in the surface layer is beneficial from the point of view of fatigue resistance, increased roughness has a detrimental effect. Accumulated energy was hereby shown to have a higher effect compared to the maximal energy applied to the specimens.

Investigation on radiation interactions with some quenched alloys used in nuclear reactors.

This study presents the investigation of the radiation interaction properties for SS304 and Incoloy 800H alloys, which are widely used in PWRs and HTGRs. First of all, theoretical and MC simulation evaluations are performed, then experiments are conducted for further analysis. The findings indicate no significant difference in mass attenuation coefficients (MAC) and gamma-ray radiation protection efficiencies (RPE) between the two alloys. Additionally, both SS304 and Incoloy 800H exhibit similar neutron shielding capabilities, with comparable effective removal cross-sections and numbers of transmitted neutrons at different neutron energies (0.025eV, 100eV and 4.5MeV). The study also examines secondary radiation generated by neutron interactions. The impact of thermal treatment (300°C, 500°C, 700°C and 1000°C) and cooling approaches (quenching and self-cooling) on these alloys were further experimentally examined. Notably, thermal treatment changes the MAC values, particularly at 1000°C, with SS304 showing a more distinct change than Incoloy 800H. Besides, quenched samples have higher MAC values compared to self-cooled samples, especially at 1000°C. However, the microhardness values remained largely unaffected by heat treatment, except at 1000°C, where both alloys exhibited reduced microhardness. The study underscores that there is no significant difference in microhardness between quenching and self-cooling techniques. These results provide valuable insights for enhancing the safety and efficiency of radiation shielding materials in nuclear reactors.

Структурна анізотропія у виробах 3D-друку за технологією селективного лазерного плавлення

Using the Ti-6Al-4V alloy as an example, the influence of thermal conditions in 3D-printing on the anisotropy of its microstructure, phase composition, residual macrostresses, and mechanical properties during selective laser melting (SLM) is demonstrated. A fiber ytterbium laser with air cooling and a nominal power of 200 W, a laser beam diameter of ~45 µm, and a wavelength of 1070 ± 2 nm was employed, with a scanning speed of 500 mm/s, a layer thickness of 25 µm, and a hatch distance of 150 µm. It is shown that the synthesized microstructure consists of periodic scale-gradient layers with a banded structure, which results from the cyclic thermal history experienced by the SLM sample of Ti-6Al-4V, rather than from segregation or oxidation. The bands exhibit a Widmanstätten α-colony morphology with an average size of structural elements around (0.2–2) µm, while the nominal microstructure between the bands shows a basket-weave morphology. The gradient width of each band is determined by thermal effects, particularly the maximum heating temperature and cooling rate from this temperature, depending on the band’s position – whether in the lower, middle, or upper part of each layer and the distance of this layer from the substrate. The cooling rate of the deposited layer decreases as the number of added layers increases and is highest at the top plane of the SLM sample due to additional heat loss from convection and radiation, as well as the absence of remelting and thermal cycling experienced by the previous layers. As a result, the microstructure of the top plane is finer, and a greater probable amount of needle-like α'-martensite, a smaller OQR size, and a higher degree of deformation of the β-phase crystal lattice provide a higher microhardness value than in the lateral plane, despite the greater magnitude of tensile macrostresses. The obtained results convincingly demonstrate the feasibility of applying thermomechanical post-processing to ensure a homogeneous structure in SLM products.

Зв'язок хімічної мікронеоднорідності сірого чавуну та структури пластинчатого графіту

The relationship between chemical microheterogeneity of gray cast iron castings, revealed by the method of color etching in sodium picrate, and the structure of flake graphite was studied. The results of microstructural studies indicate that the crystallization of gray cast iron is accompanied by the emergence of several levels of chemical and structural microheterogeneities of the crystallizing melt, affecting the formation of graphite. Microstructural features indicate that the cast iron melt, which is close in carbon content to the eutectic composition, acquires a dendritic and cellular structure before the formation of graphite. The intensity of chemical microheterogeneity and its topology are hereditarily related to the location, size and shape of graphite inclusions. Flake graphite formed inside and on the periphery of melt cells has different structure and thickness of plates. The enrichment of areas of cast iron melt with silicon leads to the formation of dendrites of primary austenite and primary graphite of the largest size in them. The microhardness of ferrite in the dendrites of former primary austenite is approximately 1.5 times greater than the microhardness of ferrite in areas adjacent to inclusions of primary graphite. A close inverse correlation (r = –0.93) was established between the microhardness of ferrite in areas with different liquation intensities and the thickness of graphite flakes located in these areas. The greatest spread of microhardness values and width of graphite flakes is observed in the most liquated areas enriched with silicon in the center of the cells, corresponding to the location of eutectic colonies. In the spaces between the cells, graphite is observed with the smallest thickness of the flakes, which are located at the smallest distance from each other. It is necessary to continue research into the hereditary influence of the structure and physical and chemical properties of high-carbon iron melts on the mechanism of graphite formation and the features of its structure in cast irons.

Determination of performance properties of galvanic coatings based on cobalt

Abstract. Problem. An effective solution to the problem of the durability of construction materials is the application of protective coatings, which allow tosignificantly expand the scope of use and service life of products. The purpose of the work was to determine the performance characteristics of electrolytic coatings with Co-Ni-Zr alloy, namely adhesion and microhardness. Methodology The microhardness of the coatings was determined by the indentation depth of the diamond pyramid. Coating adhesion was determined by the fracture method. The chemical composition of the obtained coatings was determined by the X-ray fluorescence method using the SPRUT portable spectrometer. The analysis was carried out at least in 3 points with subsequent averaging of the obtained values. Electrodeposition was carried out with a unipolar current in stationary and pulsed modes (ti/tр=2/2) while varying the current density. Originality. There are no signs of delamination of the coatings on the sandpaper, which emphasizes strong adhesion to the base. The results of metallographic studies proved that Co-Ni-Zr coatings have good adhesion to the substrate material and retain it under mechanical loads. The highest value of microhardness – 850.0 MPa was obtained in the galvanostatic mode at i = = 6 A/dm2, while the zirconium content in the alloy is 1.5 wt.%. From the results of the experiments, it can be concluded that the zirconium content does not affect the microhardness of the Co-Ni-Zr coating. When the current density increases, the microhardness of the deposit decreases, which can be explained by reaching the maximum density of the deposition current. The optimal deposition current density for the galvanostatic mode is 6 A/dm2, pulsed 6 A/dm2 for obtaining coatings with high microhardness

Evaluation of the Mechanical Properties of Different Dental Resin-Based Materials After Submersion in Acidic Beverages.

Background: The aim of this study was to evaluate the influence of acidic beverages on the mechanical properties of various dental resin-based materials. Methods: A total number of 160 samples were prepared using four types of resin-based materials-Group A (n = 40): flowable composite, Group B (n = 40): heavy-flow composite, Group C (n = 40): resin-based sealant and Group D (n = 40): nano-hybrid composite. Then, the samples were distributed into four subgroups according to the submersion solution: a (n = 10): artificial saliva, b (n = 10): coffee, c (n = 10): cola and d (n = 10): red wine. The Vickers microhardness, Young's modulus of elasticity and scratch resistance were assessed using a CETR UMT-2 tribometer. Results: The obtained results showed that 14-day submersion of the resin-based materials in coffee, cola and red wine solutions significantly (p < 0.05) decreased the microhardness values (VHN), Young's modulus of elasticity and scratch resistance. Fourteen days of storage in coffee decreased the microhardness values of flow resin from 117.5 to 81.59 VHN (p < 0.001) whereas the values of the nanohybrid resin decreased from 125.5 to 89.4 (p < 0.001). The elasticity modulus of the heavy flow resin showed a decline from 15.57 to 10.50 GPa after 14 days' submersion in coffee (p < 0.001), and from 21.29 to 13.10 GPa for the nanohybrid resin after immersion in cola (p < 0.001). For the scratch test, the resin-based sealant showed a significant decrease after 14 days of storage in coffee, from 0.34 to 0.02 units. Conclusions: The submersion of conventional nanohybrid, flowable, heavy-flow composite resins and resin-based sealants in coffee, cola and red wine solutions changes the mechanical properties (Young's modulus of elasticity, Vickers microhardness and scratch resistance). The most resistant resin-based material to acid attack was the conventional nanohybrid composite resin, followed by heavy flow resin, flowable resin and resin-based sealant.

Microhardness of single crystals of paratellurite

The values of microhardness of samples of single crystals of paratellurite differing from each other in growth conditions and structural quality were measured. For the plane (110), these values lie in the range — 300—470 kG/mm2. It has been determined that mechanical stresses in paratellurite can lead to significant deviations of values of microhardness from average values.

Effect of binary Al-Ni alloy on the rate of abrasive wear of ultra-high molecular weight polyethylene

The paper investigates the influence of the content of Al-Ni alloy quenched from the molten state on the abrasive wear rate of ultra-high-molecular-weight polyethylene on rigidly attached abrasive particles. Studies have shown that the addition of 5–30 mass% of the quenched aluminum alloy to ultra-high-molecular-weight polyethylene reduces the rate of abrasive wear by ~50%. The improvement of this indicator is due to the high values of microhardness, dislocations density, and microstresses of rapidly quenched Al-Ni alloys.

Use of Ultrasound to Identify Microstructure-Property Relationships in (AlN + WC) Fabricated with Electroless Ni Producing

In order to improve the properties of the materials produced by the powder metallurgy method, first of all, powders (16.59% AlN + 6.63% WC) were coated with nickel (Ni) by electroless method, and then box boriding, which is one of the most widely used surface coating methods, was applied. A composite formed with (16.59% AlN + 6.63% WC)76.7Ni was prepared under the Ar shroud in the temperature range of 1000-1400°C. Pulse-echo technique was used for ultrasonic velocity measurements on Ni coated (16.59% AlN + 6.63% WC) samples. It is aimed to examine the change of physical, mechanical and ultrasonic properties of the obtained ceramic-metal composites depending on different sintering temperatures. In addition, the samples were characterized by mechanical and metallographic examination. The results show that the longitudinal and transverse ultrasonic velocity values and ultrasonic modulus (shear, bulk, Young’s etc.) values increase simultaneously with the increase of sintering temperature. The highest microhardness value was observed in composite samples sintered at 1400°C and its value was 1150.80 Hv. The increased strength is mainly due to grain refinement and strong interfacial bonding between Ni particles and AlN and WC matrix.

Structural-phase state and properties of 56GM/(W + WC(Ni)) composite alloy obtained by wire electron beam additive manufacturing

The authors investigated the microstructure and mechanical characteristics of 56GM steel-based composite produced by wire electron-beam additive manufacturing with the addition of W + WC(Ni) powders during printing. The analysis demonstrates that 56GM/(W + WC(Ni)) composite alloy is characterised by a gradient structure consisting of 56GM base layer, 56GM – 56GM/(W + WC(Ni)) intermediate layer and 56GM/(W + WC(Ni)) composite layer. The base layer of 56GM steel is characterized by a multidirectional acicular structure, which corresponds to the ferrite-martensite state. In 56GM – 56GM/(W + WC(Ni)) intermediate layer the acicular structure becomes less pronounced. In 56GM/(W + WC(Ni)) composite layer an equiaxed grain structure is formed, with an average grain size of 8.59 μm, along the boundaries of which cracks are observed. WC particles are located mainly along the boundaries of small grains and in small quantities inside the grains themselves. It was found that 56GM/(W + WC(Ni)) composite is mainly composed of α-Fe (~80.6 vol. %), Ni (~6 vol. %), WC carbide phase (~10.3 vol. %) and γ-Fe (3 vol. %). The structure and properties of initial 56GM steel change both in the area of direct addition of alloying powder and in the underlying layers due to diffusion processes and infiltration of W + WC(Ni). Microhardness values increase from ~3.5 GPa to ~6.5 GPa with distance from the substrate to the composite layer. In uniaxial tensile tests, the ultimate tensile strength and yield strength values reached 1100 – 1200 MPa and 835 MPa in the intermediate layer, respectively.

Effect of TMAB and ZrC concentration on mechanical and morphological properties of Ni–B/ZrC composite electrodeposition

Abstract Coating of metal or nonmetallic materials made conductive can be achieved by electrodeposition method. Metals with low conductivity and cost, such as copper or steel, can be coated with materials with higher hardness, corrosion, and wear resistance, such as nickel and boron, and can meet the relevant requirements according to their usage areas. In this study, the impact of trimethylamine borane complex (TMAB) and zirconium carbide (ZrC) contents added to the bath concentrate in the Ni–B/ZrC composite coating applied on copper on the surface properties of electroplating was investigated. Electroplated specimens were examined with regard to mechanical, morphological, and corrosion resistance. The highest microhardness value was obtained in the coatings obtained with 6 g L−1 TMAB and 4 g L−1 ZrC bath concentration, and this value was found to be 1,020.4 H V. When examined in terms of coating morphology, it was seen that as the amount of TMAB increased, the ZrC content decreased over time. In the nanocomposite coating with 4 g L−1 ZrC concentration, which showed the best corrosion performance, the corrosion current decreased by 70 % compared to the Ni–B alloy.